1. Field of the Invention
This invention relates to a device and method for sealing the area between an indexing primer magazine and barrel-type gun system. More particularly, an insert within a gun spindle of a breech assembly seals the indexing primer magazine and breech assembly. Most particularly, the insert has a formed recess therein with a face seal housed within the recess to minimize metal to metal contact and increase the service life of the indexing primer magazine. The present invention may be used with several types of indexing primer magazines, such as drum indexing mechanisms.
2. Brief Description of the Related Art
Large gun systems generally have a breech assembly with a movable breechblock. In a closed position, the breechblock defines a passage between a positioned primer cartridge and loaded propellant charge, permitting open communication between the two. The gun systems are fired by inserting a primer cartridge into the breech assembly after loading a projectile and propellant charge into the gun. The primer cartridge may be inserted into the breech assembly by hand, however, automated gun systems insert the primer cartridge with an indexing primer magazine. The indexing primer magazine retains multiple primer cartridges, and indexes an unfired primer cartridge into a firing position with the expulsion of a previously fired primer cartridge. After an individual primer cartridge is positioned by the indexing primer magazine to fire into the breech assembly of the gun system, the positioned primer cartridge is struck for firing. The fired primer cartridge produces hot combustion gases that flow through the passage in the breech assembly until contacting the loaded propellant charge in the gun. On contact, the gases ignite the propellant charge which in turn fires the projectile from the gun.
The indexing primer magazine is located at the rear surface of the breech assembly, and provides a rapid and readily available source of primer cartridges to the breech assembly. Firing the propellant charge with the primer creates a severe environment in the vicinity of the primer feed mechanism from the hot gases resulting from the combustion of the propellant charge. Difficulties with the indexing primer magazines include maintaining a tight gas connection between the magazine holding the primer cartridges and the flow passage of the breechblock. When individual primer cartridges are fired, increased pressures and temperatures are created within the breech assembly. Gas pressures of up to 60,000 psi, and temperature of up to 3000xc2x0 K., are encountered within the flow passage. These pressures are retained within the breech assembly to ensure proper indexing of the indexing primer magazine. The pressures are retained with the breech assembly to ensure a safe environment for the soldier and to prevent damage to primer feed mechanism components. As such, the interface between the breech assembly and indexing primer magazine needs to be effectively sealed, i.e., retain the repetitious high pressures and temperatures of the hot combustion gases of the primer cartridge and fired propellant in an operational environment, such as a battlefield. The seal needs to be reliable over multiple firings as escape of the high pressures from the flow passage presents a danger to local personnel and equipment. Failure to provide a reliable seal between the magazine and breech faces may ignite adjacent unspent primers, thereby causing weapon misfires and damage to the primer feed mechanism, making the weapon unusable until it can be serviced. This failure also significantly decreases the service life of the gun system. More importantly, an unreliable seal can create a dangerous environment for the gun crews required to fire the weapon, resulting in possible injury or death.
Seals to retain the high pressures formed within the flow passage have been previously disclosed. For example, U.S. Pat. No. 5,535,660 to Zierler, entitled xe2x80x9cBreech Closure for a Barrel-type Firearmxe2x80x9d, issued on Jul. 16, 1996, discloses one method for retaining the high pressures. The Zierler patent discloses a sealing system that accommodates high and low pressures within the flow passage. However, several problems are encountered with the breech closure disclosed in Zierler, which include seal leakage, over time, from metal-to-metal contact, and steel erosion from heat checking of the magazine. For the metal cup seal disclosed in Zierler to operate properly, the primer hole on the drum component must be smaller in diameter than that of the hole in the cup, since the cup is self-energizing and slightly conical in shape, i.e., similar to a Belleville spring. This feature exposes the periphery of the drum hole to damage from being in the direct path of the hot primer gases. As the metal seal is extremely sensitive to sealing surface imperfections, the heat checking creates a source of premature seal failure. Heat resistant coatings improve, but do not eliminate, the heat stress. Live fire testing on howitzers having a mechanism such as that disclosed in the Zierler patent results in severe heat checking on the drum surface and the underside of the metal cup seal surface, which has resulted in leak paths for the created hot propellant gases. These problems decrease the longevity of the magazine and safety of the equipment.
In view of the foregoing, there is a need for improvements in the sealing the indexing primer magazine with the breech assembly in a gun system. The present invention addresses this and other needs.
An object of the present invention is to provide a reliable and effective seal between the breech assembly and indexing primer magazine while minimizing metal to metal contact of the gun system.
The present invention includes an insert for sealing an indexing primer magazine and breech assembly of a gun system comprising an elongated body having a central bore extending therethrough from a first open end to a second open end thereof, the insert being positioned with the first open end in a gun spindle of the gun system and the second open end extending outside of the gun spindle, the second open end of the elongated body having a flat surface perpendicular to the central bore, wherein the central bore is approximately centered within the flat surface, a recessed area formed within the flat surface and circumferentially surrounding and outside of the central bore, the recessed area comprising at least an inner extension and outer extension of the elongated body such that the inner extension defines the distance between the central bore and recessed area, and a face seal fixed within the recessed area, wherein the face seal forms direct contact to the indexing primer magazine.
The present invention also includes a method for sealing an indexing primer magazine and breech assembly comprising the steps of providing an insert fixed within the breech assembly, the insert having an elongated body having a central bore extending therethrough from a first open end to a second open end thereof, the insert being positioned with the first open end in a gun spindle of the gun system and the second open end extending outside of the gun spindle, the second open end of the elongated body having a flat surface perpendicular to the central bore, wherein the central bore is approximately centered within the flat surface, a recessed area formed within the flat surface and circumferentially surrounding and outside of the central bore, the recessed area comprising at least an inner extension and outer extension of the elongated body such that the inner extension defines the distance between the central bore and recessed area and a face seal fixed within the recessed area, wherein the face seal forms direct contact to the indexing primer magazine, adjusting the insert to press the face seal against the indexing primer magazine and initiating the primer within the indexing primer magazine to fire the gun.
Additionally, the present invention includes an indexing primer magazine that forms a seal with a breech assembly comprising a supporting body forming at least one opening effective to house a primer cartridge, the formed opening extending through the supporting body at the discharge head of the primer cartridge effective to longitudinally align the primer cartridge within the supporting body along the axis of a formed bore within the breech assembly, at least one recessed area formed within the supporting body and circumferentially surrounding and outside of the formed opening through the supporting body, the recessed area comprising an inner extension and outer extension of the supporting body such that the inner extension defines the distance between the formed opening through the supporting body and the recessed area and a face seal fixed within the recessed area, wherein the face seal forms direct contact to the breech assembly.
Furthermore, the present invention includes a sealed indexing primer magazine and breech assembly product formed by the process comprising the steps of aligning a primer opening formed within a indexing primer magazine with the central bore formed within a gun insert to form a conduit therethrough and locating a face seal between the indexing primer magazine and insert, wherein the face seal is separated from the formed conduit such that increased pressure within the conduit flows into the face seal and forces the face seal to seal the area between the indexing primer magazine and breech assembly.
Other and further advantages of the present invention are set forth in the description and appended claims.